Bright nickel plating baths



United States Patent '0 3,170,855 BRIGHT NICKEL PLATING BATHS Harry Kroll, Kent County, R.I., assignor to Sarki Research and Development Corporation, a corporation of Rhode Island No Drawing. Filed Mar. 18, 1963, Ser. No. 266,068

10 Claims. (Cl. 204-49) This invention relates to compositions of matter and to nickel electroplating baths and processes for the production of bright, adherent, and especially ductile nickel plates.

It is an object of this invention to provide a process for producing improved nickel plates, i.e., plates having improved ductility. Another object of this invention is to provide superior baths for electrodepositing smooth, bright, and ductile nickel. The invention also contemplates providing additive compositions useful for processes for electrodepositing smooth, bright, and ductile nickel.

I have discovered that when compounds corresponding to the formulas in Group I and mixedwithcompounds corresponding to the formula of Group II in about equimolar proportions but generally within a ratio of about one mol to not more than about 2 moles of the other, that is molar percentages preferably at the level of 50% of each but variable'to 33%% of one to 33 /a% of the other, a substantial improvement in the performance of the primary brightener effected is achieved observable largely through the greatly improved ductility of the new plate. That is with essentially conventional bath formulations using either the Watts type or the high chloride type bath with essentially the conventional sulfur compounds present as auxiliary brighteners, this mixture of special selected quaternized heterocyclic nitrogen compounds is unusually effective in achieving the. final effect.

GROUP I COMPOUNDS Compounds coming within Group I have formulas given by the following:

I ll R i(0R) OP(0R),

Pyridiniurn compounds quinolinium compounds R N O Isoqulnolinlum compounds In the above representations, R is an aliphatic group saturated or unsaturated, having from one to four carbon atoms, for example, methyl, ethyl, propyl, butyl, ally-l and methallyl, R may be hydrogen, i.e., no substituent on the ring, or an aliphatic group of one or two carbon atoms, such as methyl,. ethyl, or vinyl, and may be substituted in any position of the pyridine, quinoline, or isoquinoline ring or rings. Of outstanding utility are the N-allyl quinaldinium diallyl phosphate, N-allyl 2vinylpyridinium diallyl phosphate, N-ethyl isoquinolinium diethyl phosphate, N-butyl 4-vinyl pyridinium dibutyl phosphate, and mixtures of the pyridinium and quinolinium and quinaldinium N-alkyl dialkyl phosphates. It should be noted that Z-methylquinoline is quinaldine and the 3,170,855 Patented Feb. 23, 1965 nomenclature herein reflects this in use of quinaldinium to identify the Z-methyl quinoline moiety.

GROUP II COMPOUNDS Compounds coming within Group II have a formula given by the following:

R Br,Cl Pyridlnium compounds In the above representation, R is an allyl or methallyl group, R" is vinyl, and may be substituted in the 2 or 4 position of the pyridine. Of outstanding utility are the N-allyl-2-vinyl pyridinium bromide, N-allyl-4-vinyl pyridinurn bromide, and mixtures thereof; the corresponding chlorides are also useful; and, also, the corresponding N-methallyl-Z-vinyl pyridinium bromide and chloride as well as the N-methallyl-4-vinyl pyridinium bromide and chloride are useful.

It should be noted that in developing the preferred ratio of compound or compounds from Group I with Group II, if a mixture from one group is used the total mole percentage of compounds from that group is, preferably 50%, but within the one-third latitude defined.

In my copending applications 266,032, and 266,063, which may be considered fully incorporated herein, I have described in detail the method of synthesis of these compounds. The reaction is a direct quaternization involving stoichiometric amounts of reactant, and the technique involves precautions to avoid explosive reaction rates induced by. the exothermic character of the reaction.

These. combinations of compounds from Groups I and II are unusually potent primary brighteners in nickel plating baths. Preferably they are used in total amounts between about 0.001 and 0.30 gram per liter.

Brighteners used in nickel plating are commonly classified broadly as primary brighteners which increase the brightness of the ordinary dull or matte deposit of nickel but do not bring out the true mirror-bright condition. The secondary brighteners improve the ductility of the plate. The secondary brighteners with which this invention is primarily concerned are used in combination with these primary brighteners to develop true mirror-bright deposits. The combinations of heterocyclic nitrogen compounds as described in this present invention are potent and extraordinarily elfective secondary brighteners. The preferred concentrations are quite low, and inasmuch as these compounds are usually of quite limited solubility in water the concentration, even though low, can be readily maintained. .1 have found that the combination are unusually effective for developing ductile plates which can be shown qualitatively and semiqualitatively simply by plating a length of wire and comparing the number of times it can be flexed or bent without losing or having the plating peel. Where the ordinary brighteners are used detachment of the plate occurs quickly, whereas with my combination of brighteners the wire can be bent to the point where it could break without having the plate become detached. This test can be used on a qualitative basis for control purposes in a plating shop and by controlling conditions under which conducted it could also be used as a quantitative control and measure of efficiency of the solution.

These heterocyclic nitrogen brighteners are used in as solution together with certain sulfur compounds in concentrations of about 0.1 to 80 gram per liter. These brighteners are water-soluble sulfur compounds in which the sulfur atom has an equivalence of +4 or +6 and are selected from the group consisting of aliphatic unsaturated sulfonic acids, mononuclear and binuclear aromatic sulfonic acids, heterocyclic sulfonic acids, mononuclear aromatic sulfinic acids, aromatic sulfonamides and sulfonimides (see Table II herein). The Water soluble alkali metal, ammonium, magnesium, and nickel salts of the above compounds are used in combination with the quaternary nitrogen cyclic compounds in accordance with this invention.

The mixed brightener additives characterizing this invention, that is the mixtures of compounds from Groups I and II were evaluated ina Hull cell using a standard Watts type bath containing 330 grams of nickel sulfate heXahydrate/liter, 45 grams of nickel chloride per liter, 37.5 grams per liter of boric acid, operated at a pH of 3.5, and a temperature of 50 C. The nickel deposits were made on brass Hull cell panels 2" by 3" by plating for five minutes at three amperes. The concentrations and combination of organic additives which gave brilliant mirror-like deposits of nickel over a wide current density range are listed in Table HI.

The brighteners in accordance with this invention are useful in the conventional Watts type bath and also high chloride baths noted as follows.

WATTS-TYPE BATHS Nickel sulfate 200' to 400 g. l.

Nickel chloride 30 to 75 g./l.

Boric acid 30 to 50 g./l. Temperature 3-0 to 65 C.

pH 2.5 to 4.5 electrometric.

With agitation.

The plating conditions employed with baths of these formulations are those commonly used and reacted in plating products. Generally the working temperature of the bath will range between 40 and 70 C. The pH value will be held between about 355 and 5.0. Close control of pH in some shops calls for holding it at about 4.0 but in a range between 3.8 and 4.5. The current density will of course vary in the shape of the piece and its size and the load at which it is desired to produce in the shop, but generally it will between 1 and amps. per sq. dcm. Current densities commonly employed with Watts type baths will generally be about 4 to 7 amps, per sq. dcm., and current densities for the high quality type baths will generally be between'S and 10 amps, per sq. dcm.

Table I Propor- Concentions, tration Composition Parts Range, by Wt. grams/ liter 1 N -allyl quinaldinium diallyl phosphate... l-l N-allyl 2-vinyl pyridinium bromide 2-3 N-2-methallyl 4-vinyl pyridinium chloride. 2-3 2. N -allyl 2-vinyl pyridinium diallyl phosphate 1-1 3 {N-allyl 4-vinyl pyridinium chloride 2-3 N-ethyl isoquinolinium diethyl phosphate. 1-1 N-methallyl 2-vinyl pyridinium bromide. 2-3 0) 4. N-allyl 2-vinyl pyridinium diallyl phosphate 1-1 5 N-allyl 4-vinyl pyridinium bromide 2-3 r N-butyl isoquinolinium dibutylphosphate. 1-1 N -a-llyl 2-vinyl' pyridinium chloride 2-3 6- N-allyl 2-vinyl pyridinium diallyl phosphate 1-1 N -methallyl 4-vinyl pyridinium bromidefl 2-3 7. N-allyl 4-vinyl pyridinium diallyl phosphate 1-1 8 {N-allyl 2-vinyl pyridinium chloride 2-3 N-butyl quinolinium dibutyl phosphate.-. 1-1

1 In all examples it is kept in therange 0.001030 gram/liter.

Table II ORGANIC SULFUR ADDITIVES Concentration range,

Compound: grams/ liter Benzene sulfonamide 0.1-3 P-toluenesulfonamide 0.1-2 O-benzoylsulfonimide 0.1-1.5 O-carboxybenzenesulfonamide 0.1-2.0 Benzene sulfohydroxamic acid 0.1-2.0 N-benzenesulfonyl iminodiacetic acid 0.1-2.0 N-benzenesulfonyl iminodipropionic acid 0.1-2.0 Allyl sulfonic acid 1-10 Vinyl sulfonic acid 1-10 Sodium benzenesulfonate l-l0.0 Sodium metabenzenedisulfonate 1-10.0 1,5 naphthalene disulfonic acid 1-8 2,7 naphthalene disulfonic acid 1-8 Naphthalene trisulfonic acid 1-8 Table III Bath No.:

(1) N-allyl quinaldinium diallyl phosphate N-allyl 2-vinyl pyridinium bromide o-Benzoylsulfonimide Para toluenesulfonamide (2) N-methallyl 4-vinyl pyridinium chloride N-allyl 2-vinyl pyridinium diallyl phosphate o-Benzoyl sulfonimide (3) N-allyl 4-vinyl pyridinium chloride N-ethyl isoquinolinium diethyl phosphate Benzenesulfonamide o-Benzoylsulfonimide (4) N-methallyl 2-vinyl pyridinium bromide N-allyl 2-vinyl pyridinium diallyl phosphate Benzenesulfonamide o-Benzoylsulfonimide (5) N-allyl 4-vinyl pyridinium bromide N-butyl isoquinolinium dibutyl phosphate o-Benzoylsulfonimide Para toluenesulfonamide (6') N-allyl 2-vinyl pyridinium chloride N-allyl 2-vinyl pyridinium diallyl phosphate Para toluenesulfonamide o-Benzoyl sulfonimide (7) N-methallyl 4-vinyl pyridinium bromide N-allyl 4-vinyl pyridinium diallyl phosphate o-Benzoylsulfonirnide (8) N-allyl 2-vinyl pyridinium chloride N-butyl quinolinium dibutyl phosphate Allyl sulfonic acid In the foregoing tables for convenient reference I have tabulated the primary brighteners, secondary brighteners, and in Table III some representation of this. In general the concentration at which the brighteners are best used are practically alike in terms of weight per unit volume. Actually any of the brighteners in Table I may be used in combination with any of the brighteners in Table II. In a Watts type bath employing about 300 grams/liter of nickel sulfate, 60 grams/liter of nickel chloride and 45 grams/liter of boricacid, e.g., a variant of this bath is the high chloride type using 45 grams/liter of nickel sulfate, 250 grams/liter 'of nickel chloride, and about 45 grams/liter of boric acid. In all of these baths which I have tested virtually exhaustively in various combinations of the brighteners of Table I which brighteners of Table II, brilliant mirror-bright nickel deposits were obtained. Here the advantages obtained through utilization of the combination of heterocyclic nitrogen brighteners of Group I and Group II in accordance with this invention is in the improved ductility and brightness of the electrodeposited nickel, the improved throwing power of the bath, and the larger range of pH and temperature in which the bath maybe operated without affecting the quality of the nickel deposit. In general good electroplating practice should be followed in making the electrodeposits economically starting with clean surfaces, deposit of iron, copper, brass or other base metals conventionally used in industrial fabrication and plating at rates consistent for obtaining good adherent electrodeposits.

The foregoing tables and examples illustrate specific baths and processes, the several preferred baths being those listed in Table III, in Watts type solutions.

The nickel electrodeposits obtained from baths utilizing the novel brightener combination of compounds from Groups I and II are advantageous in that mirror-bright, lustrous, and unusually ductile electrodeposits are obtained over a wide range of current densities. The bright nickel electrodeposits are preferably plated on a copper, brass, or other copper alloy. However, they may be electrodeposited directly on such metals as iron, steel, etc., although usual practice calls for plating copper before metal.

As many embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention may be varied without departing from the scope of the appended claims.

What is claimed is: I

1. An aqueous electrolytic bath for the electrodeposition of mirror bright ductile nickel which comprises a solution containing soluble nickel salts and at least one organic sulfur compound selected from the group consisting of unsaturated aliphatic sulfonic acids, aromatic sulfonic acids, aromatic sulfonamide and sulfonimides, and a brightener consisting essentially of a component selected from (a) and (b), wherein (a) is selected from the group consisting of:

Ron and 11' R/ \OP (OR)1 R iii -orm and R R )n N/ (H) and (b) is selected from the group consisting of L R and wherein R is selected from the group consisting of methyl, ethyl,

propyl, butyl, allyl and methallyl;

R is selected from the group consisting of methyl, ethyl,

vinyl; n is 0 orl; R" is a vinyl group in the 2 or 4 position; X is a halogen. 2. As a brightener in an' aqueous electrolytic bath for depositing nickel salts in accordance with claim 1, the

1 composition which is a mixture of N-allyl 2-vinyl pyridinium bromide and N-allyl quinaldinium diallyl phosphate. 3. As a brightener in an aqueous electrolytic bath for depositing nickel salts in accordance with claim 1, the composition which is a mixture of N-allyl 2-vinyl pyridinium chloride and N-allyl quinaldinium diallyl phosphate. 4. As a brightener in an aqueous electrolytic bath for depositing nickel salts in accordance with claim 1, the composition which is a mixture of N-allyl 4-vinyl pyridinium bromide and N-allyl quinaldinium diallyl phosphate. 5. As a brightener in an aqueous electrolytic bath for depositiing nickel salts in accordance with claim 1, the composition which is a mixture of N-allyl 4-viny1 pyridinium chloride and N-allyl quinaldinium diallyl phosphate. 6. As a brightener in an aqueous electrolytic bath for depositing nickel salts in accordance with claim 1, the composition which is a mixture of N-allyl 2-vinyl pyridinium bromide and N-allyl quinaldinium diallyl phosphate. 7. The process for electroplating nickel comprising electrodepositing nickel from an aqueous nickel electroplating bath containing between 1 gram per liter and 20 grams per liter of a sulfur compound brightener, and between 0.001 gram per liter and 0.30 gram per liter of a brightener composition as defined in claim 1.

8. The process of claim 7 wherein the brightener composition is present in a concentration of between 0.001 gram per liter and 0.30 gram per liter and consists essentially of a mixture of N-allyl 2-vinyl pyridinium bromide ratio of about 2:1.

10. The process of claim 7 wherein the brightener composition is present in a concentration of between 0.001 gram per liter and 0.30 gram per liter and consists essentially of a mixture of N-allyl 4-vinyl pyridinium bromide and N-allyl quinaldinium diallyl phosphate in a molar ratio of about 2:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,893,932 Haas et al July 7, 1959 2,986,500 Passal May 30, 1961 3,054,733 Heiling Sept. 18, 1962 3,084,111

Strauss et al Apr. 2, 1963 

1. AN AQUEOUS ELECTROLYTIC BATH FOR THE ELECTRODEPOSITION OF MIRROR BRIGHT DUCTILE NICKEL WHICH COMPRISES A SOLUTION CONTAINING SOLUBLE NICKEL SALTS AND AT LEAST ONE ORGANIC SULFUR COMPOUND SELECTED FROM THE GROUP CONSISTING OF UNSATURATED ALIPHATIC SULFONIC ACIDS, AROMATIC SULFONIC ACIDS, AROMATIC SULFONAMIDE AND SULFONIMIDES, AND A BRIGHTENER CONSISTING ESSENTIALLY OF A COMPONENT SELECTED FROM (A) AND (B), WHEREIN (A) IS SELECTED FROM THE GROUP CONSISTING OF: 